On Fri, Dec 1, 2017 at 3:06 PM, L A Walsh <suse@tlinx.org> wrote:
Wol's lists wrote:
Try running a *vanilla* early 2.4 series kernel with swap == ram. As soon as the system even *touches* swap IT WILL CRASH.
--- We are in the 4.x series, what does an early bug have to do with this issue?
In Linux I have run machines with about 30 times SWAP/RAM ratio. It worked fine - albeit slowly, of course. Yes, that amount of swap was needed, there was a memory hole in YaST that ate ram when updating.
In this desktop machine the ratio is 3.
The rule is "use as much as you like", agreed. But in order to work *efficiently*, the traditional Unix swap algorithm *needs* twice ram. It's a fundamental quirk of how it works.
---- Linux's virtual memory algorithms are not those used in Unix. I don't think you can find a "traditional Unix" system from anyone anymore. If you need kernel core dumps, then you need as much space in swap as you have in memory (for the core image). If you aren't doing kernel development and you have enough memory for your needs, swap doesn't get touched. An SSD may be faster than a hard disk, but is many factors of 10 slower than RAM. I.e. memory read/write speeds are in GB/s, while small random read/writes to an SSD will be 4 to 16 times SLOWER than listed sequential testing (comparing 4K R/W to sequential R/W on http://ssd.userbenchmark.com/). This works out to <100MB/s for an SSD swap. Translation: SSD's for swap/page are about 500-1000 times slower than using RAM.
Linda, Welcome back: I don't know why those benchmarks are so slow for the top of the line SSDs. I hit 1.5 GB/sec on my lab PC. (sequential write tests (I think, might have been read.)). X99 Motherboard. Samsung PM961 SSD The PM961 is a NVMe SSD. It plugs directly into the MB. No SATA/USB involved. If your MB doesn't have a M.2 NVMe slot, you can buy a PCIe adapter for $25 or so. You can't boot off a NVMe SSD in an adapter in general. But you can when the NVMe SSD is plugged directly into the MB. Highly recommended. High-end laptops now have NVMe SSDs integrated in. I didn't test it with random i/o, so I don't know what that would be like. Greg -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org